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Old Oct 01, 2004, 02:43 PM
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Colwyn Bay, North Wales, UK
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Lipos left for few weeks, now have low runtime!?!?!?

Hi, I am using kokam 2S 1500 in my micro heli, charged by an apache 1215.
Anyway, I normally charge my batts a few hours after i have run them down, so i can use it the next day without having to wait. Anyway, a few weeks ago(like 2 or 3 weeks ago) I had them all charged up, and then i found the motor in my heli was busted. So all the while when i was waitning for the parts to arrive, and find time to fix the heli, my batts were fully chaged.
So, about 3 days ago, I got my heli back up and running, but im finding that my runtimes have been reduced from about 15 minutes to probably less than three. I dont think its the motor drawing more current, becuase my throttle stick for hovering is still about the same.
I know the packs are running out, becuase I have a 2 cell lipo warning chip thingy, and after about 30 seconds flying, it starts flashing, then it becomes constant, so i land it after like 2 minutes. This low runtime is happening every time i use the packs, and ive charged them about twice each ( I have three lipos)
Its also strange becuase its not just one battery messing up, its all three, but im almost certain it is the batteries.

So, all Im wonderign is if there is something up with my batteries, or if they will be revived with time, and get back to thier normal state. Anyone had any experiences like this before? Do you think i would be able to return them to lightflightrc, which is where i bought them from?

I just hope these arent now dead, as i really like them..

Thanks a lot, Duane
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Old Oct 01, 2004, 03:13 PM
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See if you can take them back to the LHS you bought them at and see if they don't have some technical guy there that would also possibly recharge them using their own charger. Even if you did not buy them there, I am sure they will look at what the problem may be and would jump at the chance to replace your problem with something. Perhaps it's one or another battery in the chain that is bad, causing the fail light thingy to go on. I read i some other post that if that's the case, test it using a tester individually, then carefully recharge each cell individually and then recharge the pack in it's together state. Good luck.
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Old Oct 01, 2004, 03:18 PM
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It doesn't seem likely at all that all 3 of your battery packs would suddenly go bad in exactly the same way. It seems much more likely that your 2 cell lipo warning chip thingy went bad. Do you still have good power when your 2 cell lipo warning chip thingy starts flashing?

Dan
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Old Oct 01, 2004, 03:31 PM
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Thats the thing. When my batts were fine, the servos going jittery, and the lipo light coming on were a sign of the batts running low. This is the same happening now, so i dont think the chip is bad.
Also, I am in the UK, and i bought them from lightflight RC, which is in the US, but i mmight justtalke them to my LHS, and see if they can sort it out, if not, i will send the batts back.

Duane
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Old Oct 01, 2004, 04:00 PM
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The other possibility is that your system is drawing more current than before. Friction? Binding? With 30 years in the failure analysis business, the first place we would look at is the thing that was changed -- the motor.

Like Dan says, all 3 acting the same way, maybe but kind of unlikely. Perhaps a 7.2V motor was replaced with a 6V motor. Look identical but the amp draw is different.
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Old Oct 01, 2004, 05:08 PM
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Well I dont know, the old motor that buisted, is identicl to the one that i replaced it with, graupner speed 300 6V, and i bought them both from the same place.
Yeah, there might be binding, ill have a look, but then the throttle stick would have to be higher wouldnt it, and as isaid before, it is the same for hovering as before.

Duane
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Old Oct 01, 2004, 06:54 PM
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Right, copied that part of your message but it ain't working like it did before so something has changed. Don't assume anything or you could be missing the culprit.

I assume you have no way of checking the mah into a discharged battery, the current draw of the motor, or the battery voltage before and after charging...is that correct?
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Old Oct 01, 2004, 07:25 PM
Balsa to the Wall
Deep in the East Texas Piney Woods
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One word - Whattmeter.



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Old Oct 01, 2004, 07:33 PM
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Quote:
.......and then i found the motor in my heli was busted. So all the while when i was waiting for the parts to arrive, and find time to fix the heli, my batts were fully chaged.

So, about 3 days ago, I got my heli back up and running, but im finding that my runtimes have been reduced from about 15 minutes to probably less than three. I dont think its the motor drawing more current, because my throttle stick for hovering is still about the same.
So, you changed your motor, and sudenly three packs went bad....?

In my schooldays, theheadmaster would have come down and slapped me rounfd the head and yelled 'what is that thing between your ears for. Think Boy.! Use your intelligence'

Whicjh is more likley?

Three packs suddenly going bad, or something like a high resistance joint in the wiring post motor change?

Or was it the high resistance joint that made the last motor appear 'bad'

get a voltemeter on those packs on and off load.

Check the packs, then the voltage the other side of the conector to the ESC..
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Old Oct 01, 2004, 07:58 PM
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United States, CA, Norwalk
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The most likely cause of your problem will be
battery connectors (what kind of connectors are you using?)
the new motor
the speed controller
binding caused by misadjustment of the new motor
the charger

In order to completely run the batteries down in 3 minutes from a full charge, your system would have to be drawing over 25 amps. If it was drawing that much, the motor wouldn't make it even 1 flight. Are the batteries hot after a flight-much hotter than before?

The last thing I would suspect is the batteries.
Leaving your batteries charged for 2-3 weeks won't hurt them. I don't think it's at all likely that there is anything wrong with them. If you were getting 15 minute out of them before, it isn't likely that you damaged them from high current, since the average current draw would have been about 6 amps, and the batteries are rated for 12 amps continuous, 15 amps intermittents.

When graupner 300 motors burn out the brushes sometimes short together, and that may have caused a problem with the speed controller, connectors, or something else.

You need at least a voltmeter to troubleshoot this problem, and you really should have a whattmeter or equivalent if you are going to run lipolys anyway.

Forgive me if this post rambled a bit. I kept coming up with new thoughts as I was typing.

Dan
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Old Oct 01, 2004, 08:50 PM
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Speed 300 brushed motors work well only for a short while, then they either completely quit or work intermittently.

The armature can easily be burnt from an overload
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Old Oct 02, 2004, 06:03 AM
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Maybe the charger has failed or is incorrectly configured and you aren't getting a full charge.... this is common to all three sets of batteries.
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Old Oct 02, 2004, 08:38 AM
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Colwyn Bay, North Wales, UK
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Thanks for all the help and replies.
Im going to have a chat with the 'clever guy' at the place where I bought the motor from, and see what he has to say, and then maybe send the motor back to him so he can see if its OK.
Meanwhile, please continue posting help, tips and ideas that may help me.

Thanks a lot, Duane
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Old Oct 03, 2004, 04:27 AM
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bump...
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Old Oct 03, 2004, 10:18 AM
Space Coast USA
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Why are you bumping? What answer would you like?
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